Fertilizer



* i a o I sod um s1licates to Fatented Dec. 9, 1924.

UNITED STATES PATENT OFFICE.

ALFRED HUTCHINSON COWLES, 0F SEWAREN, NEW JERSEY, ASSIGNOR TO THE ELEC- TRIO 'SMELTING AND ALUMINUM 00.,

OHIO.

OF CLEVELAND, 0 1110, A CORPORATION OF FERTILIZER.

1% Drawing. Original application filed December 28, 1918, Serial No. 268,674. Divided and this application filed May 6, 1919,

To all whom it may concern:

Be it known that I, ALFRED H. Cownns, a citizen of the United States, and resident of Sewaren, in the county of Middlesex and State of New Jersey, have invented certain new and useful Improvements in Fertilizers, of which the followingis a specification.

My invention relatesto fertilizers, and is a division of my application Serial No. 268,674, filed December 28,1918.

At the present time, soils from-the decomposition of plants and manures are known to contain hydrated silica, also artificial mixtures of fertilizers, in many instances,

' contain it in indefinite amounts as an accidental impurity; Liebig, as early as 1840, from his investigations ofthe composition of the ashes of various plants, thought silica necessary as a plant food. This re.- sultedin experiments with potassium and supply silica to augment the growth, of grasses, cereals and plants containing very large percentages of silica in their skeletons.

Knop and other plantphysiologists succeeded in, growing plants with silica supposed to be absent as a. nutri'ment, and afterwards, when the law of the .minimum was proven and accepted, silica in any form was eliminated by agricultural chemists as an essental element to use in artificial mineral fertilizers. (Soil. Conditions and Plant Growth by E. J. Russell, 1915 edition, pp. 30, 48,112). v

It is now universally assumed that silica, clay, zeolites and feldspars in soils, furnish a superabundance of silica and therefore its addition as a fertilizer is unnecessary. These substances and natural silicates are so minutely warranted. By annual repeated rowths of vegetation upon double silicates, while slowly degrading to clay, furnish to soil waters soluble silica. This accumulates and is held by zeolites, vegetation and humus, and in time, an abundance of the same is in, such soils and furnishes normal amounts to successive growths. Cultivation with exhaustion of humus and annual removal of crops, exhausts the soil faster than it is replenished. Figuratively, the sponge has been removed that has accumulated and retained in sufficient amount this material which forms a large part of the natural skeletons of plants.

. My invention or discovery soluble that the assumption is ununcultivated land; hydrated Serial No. 295,083. Renewed June 24, 1924.

Cultivation also accelerates this loss through facilitating sub-soil drainage. Thus it is that soil water solutions in soils on cultivated lands largely free from humus, have become deficient in the quantity of-soluble silica that is needed for maximum plant growth; therefore:

My invention consists in designingly using variable proportions of hydrated silica con- 1 taining more than fifteen (15) per cent of water ofhydration obtained from calcium s1licates containing molecular ratios ranging from 2 :1 to 0.70:1 calcium oxide to silica, to supply deficiencies of soluble silica required'for plant growth. Such silica containing various amounts of water is securable'by the action of carbonic and other acidsand moisture upon various simple and complex silicates, artificial or natural.

It further consists in the intentional addition or formation of designed proportions of such silicates in the preparation of fertilizer mixtures or substances, either by addition of such hydrated silica or such silicates and an acid, with the intentional design of increasing or supplying intended amounts of hydrated silica to such mixtures. further embodies addingv to soils, simple or complex, calcium silicates artificially prepared, characterized in. that carbonic acid of the soil waters will decompose saidcompounds or mixtures with a liberation of hydrated silica of a more soluble type than those hydrated silicas that commonly occur in nature as minerals. The presence of other essential fertilizers such as potash, iron oxide, phosphoric acid and sodaas impurities in said complex silicates, is not to be avoided when there is a proper allowance of calcium oxide to sili a in the mixture, so that upon the action of carbonic acid and moisture,'there shall be formed a large amount of hydrated silica by their decomposition when used.

In my invention any silicate may be used in any manner so as to supply to the soil or fertilizer mixtures. designed amounts of available added soluble silica. There are certain silicates and mixtures of silicates that can be artificially prepared that will furnish a cheap source of soluble silica. To make my invention clear as to the use of hydrated silica from these specific materials, I-explain how to form them and the reason for their use.

Many suggestions have been made involving the fusion of lime with native potash minerals such as occur in granites or potash schists and green-sand marls, with a View ,to render available the potash therein for fertilizer purposes. In such attempts, it was thought necessary to use potash minerals of high potash content and only sufficient lime to displace the molecular weight proportions of potassa that were in the constitution of the potash silicates therein. It is now thought that such .processes are valueless. In these attempts, the product securedfrom, for instance, potash feldspar and lime, the design was to lock the lime in the form of an insoluble monocalcium aluminumsilicate, freeing the potassa (K 0) forsolution; It was not realizcd thatimpure feldspar and other potash mineral silicates mixed with free silica, can be treated preferably at just their slnterlng "temperature after mixing with two or up to two and one-half molecular weight proportions of lime'to each single molecular weight proportion of silica in the mixture, and that after such treatment, the action of carbonic acid and moisture on the prodnot, will 'cause the alkali aluminate necessarily formed to decompose with liberation of potassium carbonate, and also will decompose all excess of di-calcium silicate, with the liberation of soluble calcium bicarbonate and hydrated silica. The residue left after long soil leaching, will, for example, be a calcium potassium zeolite containing in its constitution a variable fraction of a molecule of calcium oxide and a, variable fraction of a molecule of potassium oxide (annnonium and other alkalimetal oxides may form a part of this fraction) one molecule of alumina and ultimately two molecules of silica together with water of chemical combination, the quantity of which inversely varies to a marked degree with temperatures to which soil waters are naturally subjected. These substances are the hydrated feldspars or zeolites of nature. They are permutites, and when immersed in a mixed solution, like soil waters they reciprocally exchange.

specially alkali earth metal oxides and alkai metal oxides inclusive of ammonia, These exchanges are governed by the laws of mass action as bearing upon the action of various ions, with variations of temperatures and variations of the density of difl'erent solutes. Zeolites are recognized as valuable soil constituents.

Further, as a part of my invention, is the process of manufacturing the product described which consists in treating in suitable furnaces, potash bearing silicious rocks,

.calcium carbonate such as granites, schi'sts, glauconite marls and others, or mixtures thereof, all contaming large amounts of free silica, with two and a. fraction molecular weight proportions of lime or limestone for each single molecular weight proportion of silica in said mixture, and heating it to a 'temperature not high enough to materially drive away the potash contents and securing a productto be disintegrated or powdered,

and the designed and quantitative use of In this process, iron cess of lime over the 2 to 1 ratio of lime tosilica are: First to supply one molecular weight proportion of lime to each molecular weight" proportion of alumina in the mixture, thuspreventing a small amount of silica from becoming insoluble through its forming with alumina, kaolinite (Al (),,2SiO wH O). Second, under conditions of imperfect mixing, an excess insures enough charge so that at least two molecular weight proportions of calcium oxide can combine with one molecular weight proportion of silica (SiO thus e ab-ling all the potassa to assume a soluble form as mono-potassiumaluminate. An excess of lime to si'lica over the 2 :l ratio leads to higher melting point mixtures and possible volatilization of the potassa.

In the foregoing, I have mentioned the use, in a mixture designed to sinter, of two molecular weight proportions of lime or to each single molecular weight proportion of silica. after treatment with C(l such alumina as may be present in the mixture is left free as hydrated alumina and it naturally enters into combination with hydrated silica to form hydrated alumina silicates (A1 0 2SiO wH O) or the insoluble clay substances of soils. In doing this, however, lime adheres naturally to the compound and some alkali metal oxide, therefore, if. a slight excess of lime over and. above the two molecules of (M0 to one of SiO be employed in the mixture, and if the mixture be well sintered, the alkali metal oxides will be freed (luring leaching with greater facility; and it may be supplied in excess even to the extentof an added molecular weight proportion of lime to each single molecular weight proportion of alumina in the total mixture. The tricalcium silicate is too refractory .for good economical working.

(As bearing upon the chemistry of forming a proper mixture for sintering, see my pending application, Serial No. 62.486, filed November 20th, 1915.)

lime present in all parts of the In this case. I

' My invention can also be carried out'by employing sintered or fused mixtures of lime and silica or'compounds of lime and silica preferably lower in their ratio of lime to silica than two and one-half molecular weight proportions of lime to one o-fsilica. In forming these mixtures or compounds, magnesia, carbonate, iron oxide and potash as impurities in the limestoneor silica are advantageous. Such sintered or fused mixtures can be formed'in a rotary or other suitable furnaceand by well known means, disintegrated to powders or mineral wool. So formed, it always contains a little alkali, iron .oxide and alumina as impurities; When calcium silicates areused, it is desirable to have them as low in lime content and high in silica content, consistent with economical fusion or sintering and also that will readily decompose when finely divided, by the action of carbonic acid and moisture. Economical methods of producing them are well known. Tri-calcium silicate sinters at too high a temperature and furnishes less hydrated silica, therefore, I would not recommend its use, though it will decompose by the action of carbonic acid and moisture and furnish soluble silica to the soil. The mixture of lime and silica that melts at the lowest temperature, contains a little less than one molecular weight proportion of calcium oxide to one ofsilica; .70 of molecule oflime to 1 of silica works well.- With,

too low an amount of lime in-the mixture, it ceases to be acted, upon by carbonic acid and moisture, and the use of such: should be avoided.

Hydrated calcium silicates can be pro-' duced by treating infusorial earth, best' when high in water of chemical combination, with slacked lime at ordinary temperatures: high as thirteen per cent of water. This reaction does not take place with round crystalline silica, thus native hydrate silica may, by treating with slacked lime and water, produce calcium silicates suitable for use.

If the described more soluble types of hydrated silica, or the utilizable calcium silicates, be added to a soil devoid of any one of the other essential mineral fertilizer salts, no.valuable results would beex ected. In most soils these other essential sa ts occur in greater or smaller amounts. en calcium silicate is added, there is formed calcium bicarbonate in the watersof the soil. It is known that calcium bicarbonate acting on hydrated silicates containing potassium oxide'and alumina, will liberate potassium oxide to form bicarbonate of potassium, and, therefore, the lime performs a double function of sup lying .lime to the soil waters and also solub e potassium'salts. While the foregoing is known, one must conlnfusorial earth may contain asclude that the acidproperties ofsilicic acid tend to release phosphoric acid from its insoluble combination in the soil, thus also performing a double function. For maximum growth of plants, deficiencies in all essential mineral fertilizers below that which is required for their full growths should be supplied to their soil waters in soluble form.

I have made comparative plant growthexperiments using, as a fixed factor, equal amounts by welght of calcium oxlde content in di-calcium silicate, in calcium carance of nearly all the many plants submitted tocomparativetests. Theseexperimentshave been performed bothin pots and on plots of land, and with each plant,repeated comparative experiments have, been made, and

'in many cases repeated several times. The

aggregate result of this work has proven that silica insoluble form is needed'to make up that deficiency that exists in all soils that have been submitted to long cultivation.

I find this also ltrue when 1 supply lime, silica and potash secured by taking a low grade of potash feldspar, potash micas or mixtures of the like with silica, that has been sintered with lime to furnish the two plus molecular weight proportions of lime to each single molecular weight proportion of silica in the mixture. Experiments with such a sinter, l have carried on parallel with those that have been mentioned above, and the same show, in many cases, an improvement over using the proper proportioned amount of calcium silicate or lime plus soluble silica. 1', therefore, have discovered that low grade otash containing rocks can, if properly sintered or melted with lime (or limestone) be made to give up to the soil waters, hydrated silica with potassa K 0 and most of the lime employed, whilst a part of the lime will remain to form a calcium zeolite (or the like) with a relatively lower amount off contained silica than is in any of the ure double silicate minerals of said rocks om which such zeolite or permutite materials will slowly form, by action of carbonic acid and water. I consider this of great importance. Heretofore, all efi'orts have been'in the direction of utilizing only potassa (K 9) from mineralsco-nt-aining it. High grade minerals in potassium oxide in this case are required. The proper proportioning ,of lime to silica has never been'appreciatedin these old attempts to produce fertilizers from such rocks and mineral mixtures.

Proper fineness of the materials I have mentioned when applied to the soil, can be easily appreciated by all those skilled in the art, and such fineness of division was carefully observed in using the mixtures mentioned in the competitive plantgrowth experiments already described. A fineness of 80 mesh'is favorable to good results.

Deficient 'soils may be improved as to their hydrated silica content by subjecting calcium silicates containing variable amounts of alkali metal oxide and alumina, thesilicates having: a ratio of lime to silica of two and a fraction lime to one of silica, to the action of carbonic acid and water.

I discla'im the useof soluble alkali metal silicates for application to the soil or to add to fertilizer mixtures as a source of supply of soluble silica. Plant growth experiments, long ago abandoned, made with them, have led plant physiologists into the error of considering the soluble types of silica as non-essential in the fertilization of plants. These old experiments failed for a chemical reason that has not been recognized in this art, namely: all soils, 'fer tilized or not, that are suitable for plant growth,'must contain calcium bi-carbonate or a salt of calcium. The action of soluble alkali silicates when in solution and brought in contact with calcium'salts," leads to the formation of insoluble compounds formed of lime, alkali metal oxide and silica, When these old experiments were made, as there was always employed an excess of lime, or lime salt, above that necessary to form this insoluble product, such insoluble salts formed. Therefore, when the experimenters thought they were furnishing soluble silica to the soil water, this silica Wasbeing immediately. precipitated out and so rendered non-available to their plants. The deductions drawn from their experiments were, therefore, misleading. These deductions have found their wayv into the literature of this art.

Looking up of the silica occurs even with silicates or water glass and said lime compounds. Also from the work performed by Daubree, T. Sterry Hunt and others on the reaction of alkali silicates in the artificial formation of insoluble minerals. I disclaim the use of natural mono-calcium silicates, such asiVollastonite', and corresponding mono-magnesium silicates, such as Enstatite, since they are too rare in natureto form' the basis of any commercial process and have only been the subject of scientific experiments.

Having thus fully set forth my invention and the manner in which it is to be carried'out', what I claim is A fertilizer composed of artificially prepared calcium silicate, the molecular ratio of calcium oxide -to silica being less than one of calcium oxide to one ofsllica.

Signed at 'Sewaren, in the county of Middlesex and State of New Jersey, this 25th day of April, A. D; 1919. ALFRED HUTCHIN SON COWLES. 

